research and comments on quantum physics of materials

Kagomé encore: kapellasite

A few days ago I (finally!) finished a paper with several friends – let me single out Oleg Starykh, Donna Sheng, and Shoushu Gong (how cool a name is that??!!) – on a combined analytical and computational study of a spin-1/2 kagomé antiferromagnet. It wasn’t the usual nearest-neighbor one, which seems to manage to stay controversial forever, but a less-studied variant, where a longer-distance exchange coupling is dominant. This is believed to be a good model for the mineral kapellasite. It turned out that this leads to a natural way to think about the lattice as decomposed into many constituent one dimensional spin chains. Just that insight is enough to understand nearly everything, and with a little work, make a remarkable number of very detailed – and successful – comparisons between analy
tics and DMRG computations.

I like this picture of a valence bond solid order that occurs in this model, which comes completely from analytic predictions, and matches the DMRG results extremely well.